In 1969, the English physicist Sir Roger Penrosefirst suggested that infinite energy can be extracted from a black hole. The scientist believed that only a highly developed alien civilization will be able to produce energy in the ergosphere of a black hole - the outer layer of its event horizon, where, in order to remain motionless, an object must move faster than the speed of light. Two years later, another physicist named Yakov Zeldovich suggested that Penrose's theory could be verified using an experiment on Earth, and more recently, researchers from the University of Glasgow have succeeded. Scientists have proven that the way to get the energy of a black hole really works in real life - using the Doppler effect and sound waves.
Ergosphere - the space-time region near the black hole, located between the event horizon and the limit of static.
Point of no return
Penrose believed that if you place an object in the ergosphere of a black hole, then in this unusual region of space it will acquire negative energy. But for this to work, the object must move faster than the speed of light. Penrose imagined a mechanism thatwill divide the object falling into the black hole into two parts, one part falling into the hole and the other will be removed. As explained in the official research release on the University of Glasgow website, the returns generated by this process will cause the extracted half to receive energy from the rotation of the black hole. It all sounds very complicated (and it really is), which is why in 1969 a British physicist came to the conclusion that only high-tech civilization could invent such technologies.
At the heart of the work published in the journal NaturePhysics, lies the idea proposed by Zeldovich, according to which energy can be obtained using "twisted" light waves that create energy by hitting a rotating metal cylinder, which occurs using the rotational Doppler effect. This means that if a molecule emitting (or absorbing) a photon rotates itself, then the energy of the photon emitted (or absorbed) by it can differ from the energy in the stationary case.
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However, researchers from the school of physics and astronomyGlasgow University decided to "twist" a sound instead of a light. This is because sound waves are a source of much lower frequencies, and therefore, are much more practical for demonstration in a laboratory. In the course of work, physicists developed a special installation that uses a small ring of speakers that swirl sound waves. The turbulence occurs in the same way as the waves of light should have been twisted in the theory of Zeldevich.
Light waves and the Doppler effect
Physicists describe their work as follows: twisted sound waves were directed to a rotating sound absorber from a foam disk. The microphones located at the back of the disc picked up the sound from the speakers as it passed through the disc. This increased the speed of its rotation. The authors of the study found that due to the unusual behavior of the Doppler effect, this process caused obvious changes in the frequency and amplitude of sound waves.
Recall that according to the Doppler effect, the heightthe sound of the car approaching you seems to us higher, and the moving away lower. This is because sound waves come to us with a greater frequency when the car is approaching, but with less when it passes by.
As the lead author told Big ThinkResearch by Marion Cromb, a graduate student at the University of Glasgow Physics and Astronomy School, the rotational Doppler effect is limited to circular space. This means that twisted sound waves change pitch if measured from the point of view of a rotating surface. If the surface rotates fast enough, then the sound frequency can do something very strange - for example, go from a positive frequency to a negative one, while taking energy from the rotation of the surface.
In general, the authors of the new work were ableshow that as the speed of the rotating disk increased, the pitch continued to fall until it disappeared and then returned 30% louder than before. Scientists call what was heard during the experiment “extraordinary,” adding that “waves of negative frequency can take part of the energy from a rotating foam disk, becoming louder - just like Zel'dovich suggested in 1971."
You will be wondering: Can a galactic civilization survive the end of the universe?
Of course, it’s hard to say whetheraliens have this approach to obtain energy from black holes, but scientists intend to find out whether this effect extends to electromagnetic waves and other sources. And yet, at the moment, people are not able to invent technologies that would allow us to get the infinite energy of a black hole. What do you think, in the future we will succeed? We will wait for the answer in our Telegram chat.